Electrolytic reduction cell with pivotally joined superstructure support means



Oct. 1, 1968 w. HENKIE 3,

ELECTROLYTIC REDUCTION CELL WITH PIVOTALLY JOINED SUPERSTRUCTURE SUPPORT MEANS I 2 Sheets-Sheet 1 Filed Aug. 12. 1965 INVE NTOR RICHARD W. HENKIE BY g W ATTORNEY R. w. HENKIE 3,404,082 ELECTROLYTIC REDUCTION CELL WITH PIVOTALLY JO'INED S JPERSTRUCTURE SUPPORT MEANS 2 Sheets-Sheet 2 Oct. 1, 1968 Filed Aug. 12, 1965 ATTORNEY 2% a E f f v 4 I Z n E :I H- I l 1 I. w J M 0 I M o 2 U 5 R TTILllTZ L HF V a I A C a llthr 1"}! l1 3 .R Y. M B i 4 6 1 w 8 v 4 m v. 1 V r i" WW f n l1 o w 5 m w I. m Jill; :I w I, fi v W T 4V\ m s d A a United States Patent 3,404,082 ELECTROLYTIC REDUCTION CELL WITH PIVOTALLY JOINED SUPERSTRUCTURE SUPPORT MEANS Richard W. Henkie, Oakland, Calif., assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Calif., a corporation of Delaware Filed Aug. 12, 1965, Ser. No. 479,255 3 Claims. (Cl. 204-243) This invention relates to an improvement in electrolytic cell structure. More particularly, this invention is concerned with a novel system for supporting the superstructure of an electrolytic cell, e.g., an electrolytic cell for the reduction of aluminum containing compounds.

In the production of aluminum by the conventional electrolytic process, the electrolytic cell comprises in general a steel shell, having disposed therein a carbon lining. The bottonm of the carbon lining along with a layer of electrolytically produced molten aluminum which collects thereon during operation serves as the cathode. One or more consumable carbon electrodes is disposed from the top of the cell and is immersed at its lower extremity into a layer of molten electrolyte which is disposed in the cell. In operation, the electrolyte or bath, which is a mixture of alumina and cryolite, is charged to the cell, and an electric current is passed through the cell, from the anode to the cathode via the layer of molten electrolyte while oxygen collects at the anode. A crust of solidified electrolyte and alumina forms on the surface of the bath, and this is usually covered over with additional alumina.

In the conventional electrolytic process, use has been made of two types of electrolytic cells; namely, that commonly referred to as a prebake cell and that commonly referred to as a Soderberg cell. With either cell, the reduction process involves precisely the same chemical reactions. The principal difference is one of structure. In the prebake cell, the carbon anodes are prebaked before being installed in the cell, while in the Soderberg cell or self-baking anode cell the anode is baked in situ, that is, it is baked during operation of the electrolytic cell, thereby utilizing part of the heat generated by the reduction process. The instant invention is particularly applicable to the prebake cell.

In the United States, it has been generally the practice in the aluminum industry to support the reduction cell superstructure by means of legs standing on the cell shell. In Europe, it has been the usual practice to support the superstructure by four legs resting on the pot room floor adjacent the cell. With the trend in design of reduction cells towards greater size in order to have greater or increased capacity, the problem of difierential expansion between the cells shell and the superstructure becomes more important where the superstructure is mounted on the cell shell. For example, it has been found that on a 50,000 ampere cell the cell frame expands as much as one inch from room temperature to operating temperature. With stiff, firmly anchored legs supporting the superstructure, this movement induces high stress in the support legs and superstructure and results in considerable deformity in the superstructure itself diminishing its design safety factor.

With relatively small cells, i.e., up to 50,000 amperes this differential expansion problem has been alleviated by the use of a sliding foot assembly, either lubricated or dry, at the joint between the support legs of the superstructure and the shell of the cell or a roller bearing joint at this point. Even on the smaller cells these types of joints presented some difficulties although the difficulties could be tolerated. For example, there would be some binding of the joint resulting in some slight amount of ice distortion of the superstructure. Further, powdered alumina seeping into the joint would render it ineffective due to the resultant friction. Obviously, with the trend toward increasingly larger cell sizes these present minor irritations become major as the amount of differential expansion between the shell of the cell and the superstructure increases as the size of the cell increases. Further, the trend towards automation of reduction cells requires that increasinglymore equipment be supported by or suspended from the superstructure. With this increased weight in the superstructure, deformation of the superstructure under the differential expansion conditions can cause major problems. It could even result in premature superstructure failure.

Accordingly, the instant invention is concerned with providing a novel support system for the superstructure of an electrolytic cell which has the ability to compensate for differential expansion due to large temperature differences, e.g., up to 400 F. A further advantage of the novel support system of the invention is that large amounts of dust and alumina ore can be tolerated without materially reducing the ability of the joint assembly of the invention to perform its design function. Also, an advantage of the instant invention is that no lubrication is required by the novel support system and the support system will withstand rough handling by unskilled labor.

These and other purposes and advantages of the instant invention will become more apparent form a review of the ensuing detailed description taken in conjunction with the accompanying drawings.

This invention relates to an electrolytic reduction cell of the type wherein the cell has a lining which defines a cavity adapted to contain an electrolyte, the lining being encased in a supporting shell. One or more electrodes is suspended above and within the cavity from a superstructure mounted on the shell of the cell. Means are provided for attaching one end of the superstructure to one end of the shell of the cell in distal, superposed relation thereto. The opposite end of the superstructure is supported above the other end of the shell in distal, superposed relation thereto, by a plurality of parallel legs, each of which is connected pivotally at its opposite ends to both the shell and the superstructure so as to permit reciprocating movement at that end of the shell with respect to the superstructure to compensate for thermal expansion and contraction.

The accompanying drawings illustrate the presently preferred embodiment of this invention as applied to alumina reduction cells.

FIG. 1 is a side elevational view partly in cross section with parts removed for purposes of clarity, of an alumina reduction cell embodying the principles of this invention.

FIG. 2 is a fragmentary cross sectional illustration of the joint between the support leg and the superstructure of the cell.

FIG. 3 is a fragmentary cross sectional illustration of the joint between the support leg and the shell of the cell.

Referring now more particularly to the drawings in which the same reference numerals have been applied to corresponding parts and with particular reference to FIG. 1, an alumina reduction cell 10 is shown comprising a carbon lining 12 which defines a cavity 14 adapted to contain a molten aluminum pad 16 and an electrolyte 18 consisting essentially of alumina dissolved in cryolite. Carbon lining 12 is supported by a shell 20 of suitable material such as steel, a layer of insulation 22 being provided between lining 12 and shell 20. This cell further comprises a plurality of carbon anodes 24 suspended in the electrolyte by means of anode rods or bars 26 aflixed to anodes 24 by suitable means. One suitable procedure for afiixing anodes 24 to bars 26 comprises, for example, providing a recess in the upper portion of anodes 24 substanti'ally larger than the cross section of anode bars 26, placing the lower ends of bars 26 into the recess, then pouring molten cast iron into the recess around anode bars 26 and allowing the cast iron to solidify.

Current is delivered to the cell from a suitable current source by a suitable anode bus conductor 28 through anode support bus conductors 30 and bars 26 to anodes 24. Anode support bus conductors 30 are fabricated from a suitable high electrical conductivity material, for example aluminum. Generally anode bus conductors 30 are reinforced for mechanical strength by structural members of suitable high strength material, e.g., steel. From the anodes 24 the current passes through the electrolyte 18 and molten aluminum pad 16 to lining 12 and out through contact or collector bars 32 embedded in lining 12, flexible conductors (not shown) and cathode bus conductor 34.

Anode suspension bars 26 are affixed to anode support bus conductors 30 by adjustable means such as clamps '36.

As the lower portion of the anodes 24 are consumed during reduction operations, the anodes may be lowered by lowering support bus conductors 30 through the use of suitable lowering means 38 connected to a suitable source of power 40 for example an air motor. When anode support bus conductors 30 have reached their lowest position, it is necessary to maintain the anodes 24 in fixed position relative to the electrolyte 18 while anode support bus conductors 30 are raised to their highest position. This is necessary due to the staggering of the electrodes to avoid the necessity of changing all electrodes at once. In order to maintain the anodes 24 in such a fixed position, a suitable superstructure 42 is provided including structural members 44 above anode support bus conductors 30 and parallel thereto. Suitable members 46 are provided on structural members 44 on either side of anode bars 26. Thus, bars 26 and anodes 24 may be maintained in fixed position by clamping anode bars 26 to structural members 44 by engaging additional clamps not shown similar to clamps 36 with members 46. Clamps 36 may then be removed and bus conductors 30 raised to their highest position. When bus conductos 30 have been raised to their highest position bars 26 may again be clamped to bus conductors 30 by clamps 36 and the clamping bars 26 to structural members 44 may be removed. Anodes 24 may then be further lowered by lowering bus conductors 4.

superstructure 42 with all its appendages is attached at one end by legs 48 to one end of shell at deck plate 49 by being bolted through insulation 53 to lower pedestal 57 which is attached to deck plate 49 in distal, superposed relation thereto. The joint between leg 48 and superstructure 42 is a permanent rigid connection. Leg 48 is joined to shell 20 through the upper pedestal 51, insulation 53, lower pedestal 57, deck plate 49 assembly. Insulation 53 may be of any suitable material, for example, Micarta or Asbestos Ebony board.

The opposite end of superstructure 42 is supported above the other end of shell 20 by legs 50, each of which is connected pivotally as by top pivot assembly 52 and bottom pivot assembly 54 at its opposite ends to both the shell 20 through deck plate 55 and the superstructure 42 so as to permit reciprocating movement of that end of the shell 20 with respect to superstructure 42 as it thermally expands and contracts.

Pivot assemblies 52 and 54 may be seen with greater clarity in FIGS. 2 and 3 respectively wherein the same reference numerals have been applied to corresponding parts.

With reference now to FIG. 2, upper or top pivot assembly 52 comprises a convex bearing 56 attached to the end of each leg 50 and a bearing support 58 mounted on superstructure 42 for example by means of box beam 80 for each leg 50. Means are provided for pinning the convex bearing 56 and bearing support 58 together such as bolt 60 and nut 62 so as to permit pivotal movement therebetween. This pivotal movement is facilitated by 4- tapered surface 64 on bolt 60. If desired, gussets 66 may be attached to superstructure 42 so that legs may not rock or pivot beyond the desired angle of movement and collapse when the superstructure 42 is set down occasionally on a place other than a reduction cell.

With reference now to FIG. 3, it may be seen that the lower or bottom pivot assembly 54 comprises a convex bearing 68 attached by any suitable means such as welding to the lower end of each leg 50 and a bearing support 70 supported on shell 20 (as shown in FIG. 1), for example, by means of upper pedestal 82 bolted through insulation 84 to lower pedestal 86 which is attached to deck plate which in turn is attached to shell 20, for each leg. Insulation 84 may be of any suitable material, for example, a compound of asbestos fiber and portland cement bonded under high pressure and impregnated with a special asphaltic insulating material and sold under the trademark, Asbestos Ebony or phenol formaldehyde laminated materials sold under the trademark Micarta. Means are provided for pinning the convex bearing 68 and bearing support together such as bolt'72 and nut 74 so as to permit pivotal movement therebetween. An alternative means for facilitating this pivotal movement is shown here, i.e., by creating a stepped surface in the pinning means by aflixing sleeve 76 to the upper end of bolt 72 by nut 78.

If desired, a pivot assembly similar to pivot assembly 54 may be provided at the joint between each leg 48 and shell 20 at deck plate 49 so that legs 48 may pivot to compensate for flexing of superstructure 42 under load.

From the foregoing description and drawings, it may readily be seen that this jointed or articulated leg, which is free to move, readily accommodates the thermal expansion of the shell of the cell without stress and strain on the superstructure. This support system requires no expensive machining in its manufacturing, no lubrication in use, no protection from dust and is not likely to be damaged by electrical short circuiting. It can 'be readily designed to accommodate temperature dilferences of up to 400 F.

While there has been shown and described hereina'bove the presently preferred embodiment of this invention, it is to be understood that the invention is not limited thereto and that various changes, alterations, and modifications can be made thereto without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. In combination with an electrolytic reduction cell of the type wherein the cell having a lining which defines a cavity adapted to contain an electrolyte i encased in a supporting shell and wherein an electrode is suspended above and within the cavity from a superstructure mounted on the shell of the cell, the improvement which comprises:

(a) means for attaching one end of the superstructure to one end of the shell in distal, superposed relation thereto; the opposite end of the superstructure being supported above the other end of the shell in distal superposed relation thereto;

('b) a plurality of parallel legs, each of which is connected pivotally at its opposite ends to both the shell and the superstructure so as to permit reciprocating movement of that end of the shell with respect to the supersturcture to compensate for thermal expansion and contraction.

2. The electrolytic reduction cell of claim 1 wherein the pivot connection between the legs and the shell of the cell comprises:

(a) a convex bearing attached to the end of each leg;

(b)a bearing support mounted on the shell for each leg; and

(c) means for pinning the convex bearing and bearing support together so as to permit pivotal movement therebetween.

5 6 3. The electrolytic reduction cell of claim 1 wherein References Cited the pivot connection between the legs and the superstruc- UNITED STATES PATENTS ture comprlsest (a) a convex bearing attached to the end of each leg; gfl lg b --E--l---- b b t t d h t t oeyea. a eanng suppor menu on e supers ruc ure 5 2,930,746 3/1960 Cooper 204 244 XR for each leg; and

(0) means for pinning the convex bearing and bearing support together so as to permit pivotal movement HOWARD WILLIAMS Prima'y Exammer' therebet-ween. D. R. VALENTINE, Assistant Examiner. 

1. IN COMBINATION WITH AN ELECTROLYTIC REDUCTION CELL OF THE TYPE WHEREIN THE CELL HAVING A LINING WHICH DEFINES A CAVITY ADAPTED TO CONTAIN AN ELECTROLYTE IS ENCASED IN A SUPPORTING SHELL AND WHEREIN AN ELECTRODE IS SUSPENDED ABOVE AND WITHIN THE CAVITY FROM A SUPERSTRUCTURE MOUNTED ON THE SHELL OF THE CELL, THE IMPROVEMENT WHICH COMPRISES; (A) MEANS FOR ATTACHING ONE END OF THE SUPERSTRUCTURE TO ONE END OF THE SHELL IN DISTAL, SUPERPOSED RELATION THERETO; THE OPPOSITE END OF THE SUPERSTRUCTURE BEING SUPPORTED ABOVE THE OTHER END OF THE SHELL IN DISTAL SUPERPOSED RELATION THERETO; (B) A PLURALITY OF PARALLEL LEGS, EACH OF WHICH IS CONNECTED PIVOTALLY AT ITS OPPOSITE ENDS TO BOTH THE SHELL AND THE SUPERSTRUCTURE SO AS TO PERMIT RECIPROCATING MOVEMENT OF THAT END OF THE SHELL WITH RESPECT TO THE SUPERSTRUCTURE TO COMPENSATE FOR THERMAL EXPANSION AND CONTRACTION. 